Prime Minister Scott Morrison says it’s likely the West Australian government will lose Clive Palmer’s court challenge to the state’s tough border stance.

The case is being heard for the third day in the Federal Court in Brisbane before being ultimately decided by the High Court.

The Queensland billionaire argues WA’s border closure is unconstitutional and damaging trade, while Premier Mark McGowan says it is necessary to protect citizens and is based on expert health advice.

The Labor leader is angry federal government experts are giving evidence, accusing the Commonwealth of helping Mr Palmer.

But Mr Morrison says the case “goes to quite serious constitutional issues on which the Commonwealth could not be silent about”.

“There are much more broader consequences of this case … beyond specifically the pandemic,” he told reporters on Wednesday.

“It is highly likely that the constitutional position that is being reviewed in this case will not fall in the Western Australian government’s favour.”

He backed Mr Palmer’s argument the constitution provided Australians free movement, saying “that should not be prevented”.

Attorney-General Christian Porter said the federal government was supportive of total border closures in the early stages of the pandemic, when there was enormous uncertainty.

But WA’s “all or nothing” approach could not be sustained.

“Ultimately the constitutional test here is proportionality,” Mr Porter told 6PR radio.

Mr Palmer seized on evidence by infectious diseases expert Peter Collignon, who has been engaged by the Commonwealth and argues in favour of “targeted quarantine” for people from states with high levels of community transmission, which is currently only Victoria and NSW.

“We have to risk stratify different populations,” Professor Collignon told the court.

Mr Palmer also seized on evidence by WA’s chief health officer Andy Robertson, who testified there was a less than one per cent chance of COVID-19 re-entering the state whether its border was closed completely or opened to jurisdictions other than Victoria and NSW.

The United Australia Party leader said WA’s blanket border closure would “destroy the livelihoods of hundreds of thousands of people for decades”.

Mr Palmer launched the action in May after he was refused an exemption to enter WA for meetings with businesspeople, Senator Mathias Cormann and potential UAP candidates for the 2021 state election.

Mr McGowan said Mr Palmer was a “very, very selfish and self-centred person … prepared to risk everyone’s health just for his own travel arrangements”.

“We just want to keep the border arrangements in place – it annoys the hell out of me that Mr Palmer and the Liberal Party want to bring it down,” the premier said.

Mr McGowan said a “travel bubble” with low-risk states relied on the strength of their border arrangements.

“We’d rather rely upon our own,” he said.

“And secondly our legal advice is we can’t pick and choose between the states.”